class Solution {
    int m, n;
    bool vis[501][501] = { false };
    int dx[4] = { 0, 0, 1, -1 };
    int dy[4] = { 1, -1, 0, 0 };
public:
    int numEnclaves(vector<vector<int>>& grid) {
        m = grid.size(), n = grid[0].size();
        for (int i = 0; i < m; i++)
        {
            if (grid[i][0] == 1)
                bfs(grid, i, 0);
            if (grid[i][n - 1] == 1)
                bfs(grid, i, n - 1);
        }
        for (int i = 0; i < n; i++)
        {
            if (grid[0][i] == 1)
                bfs(grid, 0, i);
            if (grid[m - 1][i] == 1)
                bfs(grid, m - 1, i);
        }

        int ret = 0;
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (grid[i][j] == 1 && !vis[i][j])
                    ret++;

        return ret;
    }

    void bfs(vector<vector<int>>& grid, int i, int j)
    {
        queue<pair<int, int>> q;
        q.push({ i, j });
        vis[i][j] = true;

        while (q.size())
        {
            auto [a, b] = q.front();
            q.pop();
            for (int i = 0; i < 4; i++)
            {
                int x = a + dx[i], y = b + dy[i];
                if (x >= 0 && x < m && y >= 0 && y < n && !vis[x][y] && grid[x][y] == 1)
                {
                    q.push({ x, y });
                    vis[x][y] = true;
                }
            }
        }
    }
};